Characterization or analysis of samples (e.g., thickness of a thin film, elemental and/or chemical species concentration in a thin film formed on a substrate, etc.) is necessary in the manufacture of many different types of devices (e.g., electronic and optical electronic devices). For example, it may be necessary to determine the composition of thin dielectric films (e.g., gate oxide films, tantalum nitride films, etc.) formed in known semiconductor integrated circuit devices, such as processing devices and memory devices. Increases in the density of such devices on an integrated circuit chip and reduction in device dimensions require the advancement of production processes and characterization technologies related to the materials used to fabricate such devices.
Various techniques have been used for characterization of films, e.g., to provide thickness measurements and/or to determine the concentration of trace and/or major components in such films. For example, several of such methods include ellipsometry, transmission electron microscopy (TEM), scanning transmission electron microscopy (STEM), secondary ion mass spectrometry (SIMS), x-ray photoelectron spectrometry (XPS) (also known as electron spectroscopy for chemical analysis (ESCA)), Auger electron spectrometry (AES), and other electron beam methods.
XPS, or ESCA, has been previously used to characterize thin films (e.g., ultra thin films less than 5 nanometers) such as lubricant coatings on computer hard disks with a measurement precision of 5% RSD (Relative Standard Deviation). Further, characterization of other types of films such as SiON via XPS using standard practices has resulted in measurement precisions of 0.5% to 1.0% RSD.
From any of the mentioned technique, spectral data for a sample film are obtained. Spectral peaks are also obtained for different components in the sample film. Spectral peaks are generally, electron energy counts for detected electrons irradiated from the sample film. Some means of extracting intensities are then applied to extract intensities representatives of the peaks. Such means for intensity extraction include algorithm or mathematical functions that perform basis function determination, slope analysis, peaks area calculation, Gaussian, Lorentzian, or predetermined Basis functions that can be applied to fit a spectral peak to a shape and extract an intensity value representative of such spectral peak. The extracted intensities are then used in determining the characteristic of the sample film such as film thickness, component dose and component concentration in the film.
Currently, when a spectroscopy system such as XPS is used, there has to be calibration or matching procedures for the hardware elements for all necessary systems so that the results obtained on the systems are in agreement among one another. Typically, the manufacturers perform the calibration procedures of the system. Such calibration procedures have to be done in a way that gives as close to similar physical behavior as possible among all systems. Even with the calibration done, a linear gain and/or offset correction may still need to be applied to the results on multiple systems to be used so as to get similar responses among all systems.
Under the current practice, characteristic values determination on multiple systems or tools (e.g., multiple XPS systems) require linear gain and offset correction between all systems so that the results from one system can match the results from another system.
In a simple illustration, a first film is analyzed under tools 1 and 2. The results obtained from tool 1 may yield, for example, a thickness value of 5.6 Angstroms and from tool 2, a thickness value of 6.0 Angstroms. A second film analyzed under tools 1 and 2 may yield a thickness value of 11.0 Angstrom on tool 2 and 12.1 Angstrom on tool 1. A correlation is determined for both tools (FIG. 1). A best-fit line is applied to the correlation. An offset and slope values are determined for the best-fit line. In this example,                Tool 1=Offset+Slope (Tool 2)        Slope=1.1        Offset=−1        
The slope and offset values constitute the matching error for the tools 1 and 2. Thus, under the current practice, each characteristic determination must be done prior to the determination of the matching error between the two tools or systems.
Designing and calibrating hardware elements on multiple systems (e.g., XPS systems) need to give as close to similar physical behavior as possible between the systems. A final step of applying a linear gain and offset correction to each measurement has shown to be unmanageable for broad array of possible film compositions and time consuming.